Conventionally, scroll compressors have been known as compressors for compressing fluid. For example, Japanese Patent No. 3731433 discloses a scroll compressor of this kind. The scroll compressor contains a compression mechanism in which a fixed scroll and an orbiting scroll are meshed with each other in a casing. The orbiting scroll rotates eccentrically about the fixed scroll by a motor. Thereby, the fluid sucked into a compression chamber from the vicinity of the outer periphery of the fixed scroll flows near to a discharge port on the center side of the fixed scroll while the volume of the compression chamber gradually decreases. Thus, when the compression chamber with the fluid compressed therein communicates with the discharge port, the fluid is discharged from the discharge port.
The scroll compressor disclosed in the Japanese Patent No. 3731433 includes a pressing mechanism for pressing the orbiting scroll toward the fixed scroll. Specifically, this pressing mechanism applies discharge pressure (high pressure) to the back side of an end plate portion of the orbiting scroll. This lightens the upsetting moment applied to the orbiting scroll resulting from the gas pressure (gas load in a thrust direction or radial direction) in the compression chamber.
Meanwhile, in the configuration having such a pressing mechanism, the high pressure applied to the back side of the end plate portion of the orbiting scroll increases, under the operating condition that the pressure differential between high and low pressure regions of the fluid is especially large. Therefore, the pressing force of the orbiting scroll is increased, and the sliding loss in the thrust direction between the fixed scroll and the orbiting scroll is increased.
Thus, the scroll compressor disclosed in the Japanese Patent No. 3731433 is provided with a pushback mechanism for suppressing such an excessive pressing force. Specifically, in the pushback mechanism disclosed in the Japanese Patent No. 3731433, a high-pressure inlet groove is formed in a sliding surface between the outer periphery of the fixed scroll and the end plate portion of the orbiting scroll. For example, under the operating condition that the pressure differential between high and low pressure regions is large, when high pressure lubricating oil is supplied to the high-pressure groove, a pushback force (separating force) which axially separates both scrolls is generated between the fixed scroll and the orbiting scroll. As a result, it is possible to suppress the pressing by the excessive pressing mechanism and the sliding loss in the thrust direction is reduced.